1. Field of Invention
The present invention relates to a method of aligning fiber optic arrays to integrated optical waveguide circuit components.
2. Prior Art
Integrated optical waveguide circuit devices, such as planar waveguides, lightwave optical circuits, and integrated optical devices on planar glass or semiconductor substrates are becoming increasingly important in multi-wavelength transmissions systems, fiber-to-the-home, and optical telecommunications systems.
To function, a light guiding waveguide region in the optical device must be interconnected or pigtailed with a light guiding waveguide region in an optical fiber or another optical device. The interconnection requires low loss of typically less than 0.2 dB per connection, environmental reliability against heat and humidity, and cost effectiveness. Achieving a low loss connection requires extremely high precision alignment of the light guiding waveguide regions.
One way to align the waveguide region in planar optical devices with the light guiding region in an optical fiber is by active alignment, wherein the waveguide regions of the input fiber optic array are butted together with the optical processing chip. The alignment is then monitored with an optical monitoring tool, typically a separate output fiber optic array, and the abutting waveguide regions are then secured together. U.S. Pat. No. 6,181,856; U.S. Pat. No. 6,278,814; and U.S. Pat. No. 5,559,915 are incorporated by reference herein.
Another approach is passive alignment, which involves aligning the waveguide regions by mechanical means. For example, a planar optical device may be aligned with an array of fibers or another planar device by using a pair of connector devices, fabricated by forming V-grooves on a silicon wafer that support a planar waveguide surrounded by a plastic molded connector plug. The V-grooves are precisely located on the wafer, and the V-grooves support guide pins. The guide pins are positioned to be received by guide holes on an oppositely disposed connector plug, which contains an array of optical fibers. Connection of the two plug ends passively aligns the planar waveguide and the array of fibers. Such prior methods rely on at least two precision v-groove optical fiber arrays and/or other high tolerance precision mechanical structures along with the integrated optical component to complete the assembly. The combinations of these components do not provide an economic means to precisely align arrays of optical waveguides with optimized optical coupling, due to the high cost of each individual component.